Data generated by sensors and other devices are used by various applications over a network, and shared between multiple companies. The data generated by sensors include sensing data such as, for example, temperature, humidity, altitude, wind speed, energy consumption, and positional information, which are measured periodically by the sensors. Data generated by devices include, for example, sales data from point of sale (POS) terminals or vending machines, and information related to operational status or service provision such as inventory data. The amount and types of data generated by sensors and other devices is significant. This data is stored in data centers and accessed by multiple users in multiple locations from multiple applications over a network, for example.
Methods for storing data over a network include, for example, methods for storing data in a central location over a network and methods for storing a copy of the data near each application. One method for storing a copy of the data near each application is the content delivery network (CDN).
FIG. 1 is a diagram illustrating an example of a content delivery network. According to a content delivery network P100, data is collected and stored in an origin server P1 in a data center P50. Client terminals #1 and #2 coupled to an access network P60 are located near the data center P50. A client terminal #3 coupled to an access network P70 and a client terminal #4 coupled to an access network P80 are located far from the data center P50. The terms near and far used here are determined, for example, by the amount of access time when downloading content data from the data center P50 to the client terminals #1 through #4.
For example, the content data is uploaded to the origin server P1 by the client terminal #1. When the user at the client terminal #2 accesses this content data, the client terminal #2 downloads the content data from the origin server P1.
Conversely, it takes time for the client terminal #3 and #4 to download the content data form the origin server P1 as they are located far from the origin server P1. This transfer of content data from the origin server P1 to the client terminal #3 and #4 cause an increase in the amount of traffic in the Internet.
For this reason, with the content delivery network P100, cache servers P2 and P3 are deployed near the client terminal #3 and #4, respectively, and copies of the content data are stored in the cache servers P2 and P3. In this case, the client terminal #3 and #4 access the cache servers P2 and P3, which are near, and this reduces the access delay from that regarding download from the origin server P1. Also, the content data no longer flows between the origin server P1 in the Internet and the cache servers P2 and P3 when the client terminal #3 and #4 download the content data. For this reason, the amount of traffic generated in the Internet by content data downloads from the client terminal #3 and #4 may be reduced.
Therefore, according to the content delivery network P100, the access delay and traffic increase when downloading content data may be reduced by deploying copies of the content data near the client terminals.
Japanese Laid-open Patent Publication No. 2004-126716 is an example of related art.